The rare earth or lanthanide metals comprise some 15 elements. Among them, cerium is of particular interest for several reasons. Cerium is the most abundant rare earth metal, representing about 47% of all of the rare earth metals found in the earth. It is three times more abundant than metals such as magnesium and lead, twice as abundant as cobalt and even more abundant than tin. Cerium can exist in two valence states, +3 [cerous, Ce(III)] and +4 [ceric, Ce(IV)] each possessing distinctly different chemistry and application possibilities.
The preparation of organic derivatives of Ce.sup.+4 is difficult because of the tendency to oxidize components of the reaction system which reduces cerium to Ce.sup.+3 as described in our U.S. Pat. No. 4,492,655 issued Jan. 8, 1985. Cerium (IV) alkoxides however are stable. They were first prepared by Bradley et al (J.Chem.Soc. 1956, 2260) from a process requiring the difficult preparation of ceric hexachlorodipyridinium complex. More recently a process using ceric ammonium nitrate (CAN) has been described in U.S. Pat. No. 4,489,000, issued Dec. 18, 1984.
One objective of this invention is to provide new derivatives of cerium. More particularly, one of the objectives of this invention is to prepare organo-cerium compounds in which cerium exhibits a valence of +4.
Another objective of this invention is to provide a method for preparing derivatives of cerium compounds in which the organic moiety contains an amino group.
Still a further objective of this invention is to provide a large class of novel cerium (IV) compounds which have properties suitable for use in several applications.
The new derivatives can be described as ceric alkanolatoamines. A search of the literature has failed to reveal an example of such cerium (IV) derivatives. Chloro(aminoalcoholato)- and nitrato(amino alcoholato)compounds of Ce.sup.+3 and other trivalent lanthanides have been described in Russian Journal of Inorganic Chemistry 14 (3) 1969. These cerous compounds are described to be insoluble in methanol, acetone, ether and water and to have the following formula. EQU LnCl(OC.sub.2 H.sub.4).sub.2 NH and Ln.sub.2 (NO.sub.3).sub.3 (OC.sub.2 H.sub.4).sub.2 NH.OC.sub.2 H.sub.4 NH C.sub.2 H.sub.4 OH
Reactions of metal alkoxides with alkanolamines are described in Metal Alkoxides by D. C. Bradley, R. C. Mehrotra and D. P. Gaur, Academic Press 1978, page 226-241.
In relation to the lanthanides there is the following:
"A comparative study of the reactivity of lanthanon isopropoxides viz, gadolinium, erbium, ytterbium, and yttrium isopropoxides towards ethanolamine indicated that only the hydroxyl group of ethanolamine was found to be replaceable with isopropoxy groups of these lanthanons [175, 176] thus resembling trivalent aluminum, gallium or iron analogs. The reactions with diethanolamine and triethanolamine also showed a similar behavior. All these derivatives are sparingly soluble or insoluble solids which decomposed on heating in vacuo. The bis-(diethoxyaminate) derivatives of all these elements lost one mole of diethanolamine to form bis-lanthanon tris-(diethoxyaminates) when heated under reduced pressure.